Revisiting Relationships among Specific Surface Area, Soil Consistency Limits, and Group Index of Clays

Investigations correlating specific surface area (SSA) with other soil parameters like consistency limits are helpful in understanding the internal meaning of soil properties. In this study, a large database (267 groups of test results) from the literature is established, and the performed statistical analyses show that the traditional relationship with limited data may be invalid when large data are involved. Hereafter, there is a relatively good relationship between the soil consistency limits and SSA when the threshold SSA value (about 80 m(2)/g) is identified, which suggests that the soils totally behave as pellets and platelets in the geometry, respectively, before and after this value. Despite the fact that this threshold SSA should complicatedly depend on the crystalline formation, clay mineral, and clay fraction in the particle size distribution, this threshold is relatively reliable in view of these large data statistics. Additionally, the group index by ASTM and the methylene blue value by Laboratoire Centrale des Ponts et Chaussees in France can be mutually converted to characterize subgrade soils to account for the established relationship between consistency limits and SSA.